My bras fit quite well, but I get a very small amount of bulging at the top of the cup and a very small amount of wrinkling at the bottom of the cup. It seems like there would be enough room in the cup, except the room is in the wrong place. I wear a 30G and have been suspecting a 28GG would be better anyway because my bands feel a bit loose. Any chance that would solve my problem? Or should I go up an additional cup size? It's most pronounced with my one full coverage bra but happens with some of my balconettes too. Any particular style or brand I should try? It's really not a huge problem but with the amount of money bras cost me I want them to be perfect!Unfortunately, this is't a question where I can say, "Oh, I know exactly what the problem is and you just need to do this." However, I can give you some suggestions to try. :-)
It's entirely possible that going to a 28GG or 28H would solve the problem. The rule of thumb for your best cup size is, it should be the biggest cup size you can fill out when putting it on correctly. Try putting one of your current bras on correctly, and see if you are spilling over anywhere. If so, you definitely need a bigger cup size. Regardless, if 30 is seeming loose to you I would recommend going down to a 28, since it's the band that gives you most of the support.
I also wonder if your current bras are simply the wrong style for you. Based on what you said about balconette styles, it sounds like bras with shorter (up and down) wires are better for you, so you probably want to stick to those styles. It may be that you need wider (side to side) underwires, which would make sense with what you said about the room being at the wrong place. Underwire width varies by brand and style, but you could start with the brand Panache, which generally has wider underwires as well as a good variety of bras down to a 28 band.
It is likely a combination of problems. Most people have specific styles and features that work better for them, as well as their right size. You have to keep experimenting to find what combination works for you, and then look for bras with those features. If it was possible for you to go somewhere to try on a variety of styles and sizes, that would of course make it easier to figure out what's right for you. But if that's not possible, you might just have to buy and return bras until you find the right one. It's not the most convenient solution in the world, but it should be worth it in the end!
Good luck and I hope you find your perfect bra! I would love to hear from you again once you figure out the solution. Does anybody else have suggestions for Fiona?